From patchwork Thu Apr 19 07:52:32 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 900656 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=2001:4830:134:3::11; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=redhat.com Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 40RWTB4HWwz9s1s for ; Thu, 19 Apr 2018 17:53:50 +1000 (AEST) Received: from localhost ([::1]:57319 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f94O4-0004xO-Lw for incoming@patchwork.ozlabs.org; Thu, 19 Apr 2018 03:53:48 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43297) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f94NJ-0004wI-DP for qemu-devel@nongnu.org; Thu, 19 Apr 2018 03:53:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f94NG-0002x0-9d for qemu-devel@nongnu.org; Thu, 19 Apr 2018 03:53:01 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:38518 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1f94NA-0002qG-9A; Thu, 19 Apr 2018 03:52:52 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4F6F24023150; Thu, 19 Apr 2018 07:52:51 +0000 (UTC) Received: from localhost (ovpn-116-54.ams2.redhat.com [10.36.116.54]) by smtp.corp.redhat.com (Postfix) with ESMTP id 122242156617; Thu, 19 Apr 2018 07:52:49 +0000 (UTC) From: Stefan Hajnoczi To: Date: Thu, 19 Apr 2018 15:52:32 +0800 Message-Id: <20180419075232.31407-3-stefanha@redhat.com> In-Reply-To: <20180419075232.31407-1-stefanha@redhat.com> References: <20180419075232.31407-1-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Thu, 19 Apr 2018 07:52:51 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Thu, 19 Apr 2018 07:52:51 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'stefanha@redhat.com' RCPT:'' X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.187.233.73 Subject: [Qemu-devel] [RFC 2/2] block/file-posix: verify page cache is not used X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Sergio Lopez , qemu-block@nongnu.org, "Dr. David Alan Gilbert" , Max Reitz , Stefan Hajnoczi Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" This commit is for debugging only. Do not merge it. mincore(2) checks whether pages are resident. Use it to verify that page cache has been dropped. You can trigger a verification failure by mmapping the image file from another process and loading a byte from a page so that it becomes resident. bdrv_co_invalidate_cache() will fail while the process is alive. Signed-off-by: Stefan Hajnoczi --- block/file-posix.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) diff --git a/block/file-posix.c b/block/file-posix.c index df4f52919f..d3105269c6 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -2236,6 +2236,75 @@ static int coroutine_fn raw_co_block_status(BlockDriverState *bs, return ret | BDRV_BLOCK_OFFSET_VALID; } +static bool is_mincore(void *addr, size_t length) +{ + size_t vec_len = DIV_ROUND_UP(length, sysconf(_SC_PAGESIZE)); + unsigned char *vec; + size_t i; + int ret; + bool incore = false; + + vec = g_malloc(vec_len); + ret = mincore(addr, length, vec); + if (ret < 0) { + incore = true; + goto out; + } + + for (i = 0; i < vec_len; i++) { + if (vec[i] & 0x1) { + incore = true; + break; + } + } + +out: + g_free(vec); + return incore; +} + +static void check_not_in_page_cache(BlockDriverState *bs, Error **errp) +{ + const size_t WINDOW_SIZE = 128 * 1024 * 1024; + BDRVRawState *s = bs->opaque; + void *window = NULL; + size_t length = 0; + off_t end; + off_t offset; + + end = raw_getlength(bs); + + for (offset = 0; offset < end; offset += WINDOW_SIZE) { + void *new_window; + size_t new_length = MIN(end - offset, WINDOW_SIZE); + + if (new_length != length) { + munmap(window, length); + window = NULL; + length = 0; + } + + new_window = mmap(window, new_length, PROT_NONE, MAP_PRIVATE, + s->fd, offset); + if (new_window == MAP_FAILED) { + error_setg_errno(errp, errno, "mmap failed"); + break; + } + + window = new_window; + length = new_length; + + if (is_mincore(window, length)) { + error_setg(errp, "page cache still in use!"); + break; + } + } + + if (window) { + munmap(window, length); + } +} + static void coroutine_fn raw_co_invalidate_cache(BlockDriverState *bs, Error **errp) { @@ -2270,6 +2339,8 @@ static void coroutine_fn raw_co_invalidate_cache(BlockDriverState *bs, return; } #endif /* __linux__ */ + + check_not_in_page_cache(bs, errp); } static coroutine_fn BlockAIOCB *raw_aio_pdiscard(BlockDriverState *bs,